Not Applicable
Not Applicable
Not Applicable
The present invention relates to float operated valves for controlling venting of vapor from a motor vehicle fuel tank. Such fuel tank vapor vent valves, in a typical passenger car or light truck application, have the valve outlet connected to a storage canister which is connected to the engine air inlet to purge the canister of vapors upon operation the vehicle engine.
Vapor vent valves of the aforesaid type are designed to be installed through an access opening in the upper wall or top of the fuel tank and control vapor flow through the valve outlet, which extends exteriorly of the fuel tank. Such valves are commonly float operated; and, the float is operative to close the valve outlet when the liquid fuel level in the tank is raised to the top of the tank upon refueling.
Present practice in the passenger car light truck motor vehicle manufacturing includes forming fuel tanks of a molded plastic material impervious to the fuel liquid and vapor as for example: high density polyethylene (HDPE) material.
In order to minimize fuel or vapor leakage around the valve access opening in tanks formed of HDPE, it has been desired to retain and seal the valve in the tank access opening by permanent means such as, for example, ultrasonic weldment.
However, it has been found necessary to form the valve body from structural material, which is dimensionally stable in the presence of liquid and vaporized fuel and atmospheric moisture and thus is different from the tanks material. In particular, materials found suitable for fabricating the valve body and float have been found to be non-weldable to the HDPE material of the fuel tank. Thus, it has been desired to provide an attachment for the valve body which is weldable to the fuel tank and which provides adequate sealing to prevent escape of the fuel vapors through the attachment.
Heretofore, it has been known to provide an attachment member formed of material suitable for weldment a tank formed of to HDPE material and to seal the attachment installation upon the valve body by sealing surfaces configured to provide a tortuous path of engagement between the attachment and valve body.
However, this own technique for providing a seal between the weldable attachment member for the tank and the valve body in a fuel tank vapor vent valve has been found to cause problems in service in view of the dimensional variations between the attachment and valve body as fabricated; and, expansion and contraction due to ambient temperature changes has attributed to leakage between the attachment and valve body.
Therefore, it has been desired to provide a simple, reliable and robust technique for mounting and sealing a fuel vapor vent valve on a vehicle fuel tank in a manner which prevents fuel vapors escaping to the atmosphere surrounding the tank and yet provides for weldment to the tank and is sufficiently economical to be practical for high volume mass production motor vehicles.
The present invention provides a technique for attaching and sealing a fuel vapor vent valve to a vehicle fuel tank in a manner which addresses the above-described problem vapor leakage between the attachment formed of material weldable to the fuel tank and the valve body formed of material which is not welable to the fuel tank. The valve and method of making same of the present invention employ a groove formed in the mounting flange of the valve body with a low permeation resilient seal disposed in the groove. The peripheral portion of the flange, the groove and the resilient seal are then overmolded with plastic material which is weldable to the fuel tank material. In one embodiment the annular resilient seal is formed of cured elastomer attached to a rigid ring; and, in another embodiment the resilient annular seal is formed of potting compound dispensed in the groove and cured therein prior to overmolding with material weldable to the tank.
In the presently preferred practice the over mold is formed of high density polyethylene material (HDPE); and, the valve body is formed of material selected from the group consisting of aliphatic polyketone, polythalamine, polyamide, acetal, polyester, polyphenylene sulphide and glass filled polyamide.